moved error handling related methods from app to errorhandler
improved error handler output on console app
adjusted guide and small code adjustements
cleanup web errorhandler
improved session error handling

fixes #1946
Merge branch 'master' into refactor-errorhandler

* master:
  Fixes #2912: Relative view files will be looked for under the directory containing the view currently being rendered
  app end improvement.
  improvement of Application::end() handling.
  typo fix.
  Fixes #2910: Added `Application::end()`

Conflicts:
	framework/base/Application.php
created console errorHandler
handle Exceptions in application init()
removed TODOs
cleanup application errorHandler getter
removed unnecessary static var
Merge pull request #2916 from yiisoft/refactor-errorhandler

Refactor errorhandler